iOS: We all use to-do lists for future tasks, but what about when you need to keep track of what you've already done? iOS app Time Flies keeps track of past events so you can more accurately plan what to do next.

It's a pretty simple app: instead of inputting future events, you let it know when the last time you did something was (or how many times you've done that task recently). It's useful for all sorts of things: keeping track of how often you're working out ("did I go to the gym once or twice this week?"), when the last time you got your spouse flowers was, the actual date of that car accident (for insurance purposes), or even when the last time you did anything was ("Oh man, I haven't gotten off this couch since Tuesday"). You could always use a regular old calendar for some of these things, but Time Flies is especially nice for repeating events—with the press of a button you can log in another workout session and be done with it. Hit the link to check it out.